So I was on the L4D Wiki (wishing I had the game + getting ideas for my own zombie game in Blockland) when I thought, "Hey, why not have an adrenaline shot in Blockland?" When used, it could change your playerblock to a fast one for 30 or so seconds and then change it back. When used, it could be like Bushido's Grenade + Rocket launchers, a one-time only thing thrown behind you after you use it.
imo It would be useful for more than just zombie games, it could also be used for T/DMs and RPGs.